Canal (waterway)

Formerly, when important rivers were found to be unnavigable at certain points, shallow side canals running parallel to the river were built with pick and shovel so that vessels could bypass that part of the river and reenter it at a more suitable point. With the advent of power machinery, this practice has been largely discarded in favor of canalization of the river itself; that is, a river may be dredged at unnavigable points and provided with dams and bypass locks that control the level of the river from end to end. Construction of 40 locks and dams on the Ohio River was completed in 1929; redevelopment, begun in 1955 to replace the current system with 18 high-lift locks, was completed in 1981. Canalization of the upper Mississippi River from Minneapolis, Minnesota, to Alton, Illinois (just above St. Louis, Missouri), was completed in 1939-40. In May 1954 the U.S. Congress authorized the federal government to join with Canada in the construction of the St. Lawrence Seaway; as its share of the project, the U.S. built two canals, three locks, and various other improvements along the St. Lawrence River from Montréal, Qué., to Ogdensburg, New York. Canalization of the Arkansas River, which includes 13 locks and dams and a 14-km (9-mi) canal linking the Arkansas to the White and Mississippi rivers, opened the river to navigation to Catoosa, Oklahoma, in 1970. The Tennessee-Tombigbee Waterway, a 407-km-long (253-mi-long) project that was completed in 1984, includes five dams, ten locks, and a 72-km-long (45-mi-long) canal linking the two rivers in Alabama, Mississippi, and Tennessee.

See also Dam; Intracoastal Waterway; Shipping Industry.

Ship canals are generally of two kinds: those that connect two lakes or oceans, such as the Suez Canal and the Panama Canal, and those that link an inland port to the ocean, such as the Manchester Ship Canal and the Houston Ship Channel. The accompanying table includes the major ship canals of the world.